This invention relates generally to a circuit and system for sensing the velocity of a moving object and producing a triggering pulse which is a function of distance regardless of variations in velocity.
The invention has particular application to the field of ballistics, however it will function in any situation where a moving object is able to trip two sensors and an event is to take place at a known distance from a sensor.
It is customary and well known in the arms industry, that one method of evaluating arms and ammunition is by firing a projectile through a pair of sensors. A first sensor will normally start a clock while a second sensor will stop the clock, the elapsed time is used to calculate the velocity of the projectile. Additionally, occasions arise where the projectile is to be photographed or X-rayed along the flight path. Ordinarily the general velocity of the projectile is known and a sensor is set up which triggers an instrument after an elapsed time period.
One of the major drawbacks to the aforementioned system is that due to the variations in velocity of various projectiles it is difficult to produce high quality photographs in each instance. When using ultra high speed photography which is necessary in the field of ballistics, an error of a few micro seconds could mean the difference between a good photograph, a bad photograph or perhaps no photograph at all.
Consequently, one of the major concerns is that of positioning the object to be photographed relative to the camera. The techniques of high speed photography utilize extremely short duration, low intensity light pulses with an open camera aperture. Under these conditions focus is critical in that due to the limited depth of field of the camera, where variations in the objects position may create different degrees of distortion.
The system described herein solves the object position problem by sensing the velocity of the object and triggering a light source when the object is at a predetermined position regardless of object velocity.